A paper just published in Proceedings of the National Academy of Sciences shows the impacts of nitrogen deposition in the environment may extend even further than previously thought. Dr Richard Payne and Professor Nancy Dise, of Manchester Metropolitan University, together with colleagues at Lancaster University and the Open University, studied more than 100 individual plant species' reactions to nitrogen deposition at 153 grassland sites across Europe.

ADVERTISEMENT

The scientists found that many species, particularly wildflowers such as creeping buttercup, harebell, yarrow, and autumn hawkbit, were much less abundant in areas with high nitrogen levels, such as central Britain, the Netherlands, northern Germany and Brittany. But particularly surprising was the discovery that many species declined at very low levels of pollution, often below the legally-recognised 'safe' level.

Professor Dise said: "One of the drawbacks of previous studies is that most field experiments to establish limits on pollution are near the populated and polluted areas where most scientists live. It may be that long-term exposure to even medium levels of pollution have already changed these ecosystems. In this latest research, we studied many grasslands along the natural gradient of pollution across Europe. And we found that at even relatively 'clean sites', low levels of pollution had an effect on the abundance of some plant species."

This surprising result shows that even areas a long way from pollution sources and previously thought to be free from air pollution impacts may have been affected. But this is an environmental concern that most people have never heard about. Dr Payne said: "We have been very good at communicating the problem of climate change and carbon emissions but have failed at communicating the nitrogen problem. Until the public are aware of the issue then policy makers are unlikely to take action."

The scale of the problem is huge. It has been estimated nitrogen pollution costs the countries of the European Union alone up to €320 billion a year- but progress in tackling it has been limited.

Over recent decades many developed countries have been quite successful at reducing nitrogen produced by fossil fuel burning; UK emissions of nitrogen oxides are down by almost 60% over the last 40 years. But tackling agricultural emissions has proved much more difficult. Nitrogen fertilizers are essential to feeding the world’s population but we can try to reduce the amount we use and the amount we lose into the environment.